Add flush and sync around prints

quest/src/api/channels.cpp

@@ -456,11 +456,15 @@ extern "C" void reportSuperOp(SuperOp op) {
     size_t elemMem = mem_getLocalSuperOpMemoryRequired(op.numQubits);
     size_t structMem = sizeof(op);
 
+    printer_sync();
+
     print_header(op, elemMem + structMem);
     print_elems(op);
 
     // exclude mandatory newline above
     print_oneFewerNewlines();
+
+    printer_sync();
 }
 
 
@@ -479,11 +483,15 @@ extern "C" void reportKrausMap(KrausMap map) {
     size_t superMem = mem_getLocalSuperOpMemoryRequired(map.superop.numQubits);
     size_t strucMem = sizeof(map);
 
+    printer_sync();
+
     // gauranteed not to overflow
     size_t totalMem = krausMem + superMem + strucMem;
     print_header(map, totalMem);
     print_elems(map);
 
     // exclude mandatory newline above
     print_oneFewerNewlines();
+
+    printer_sync();
 }

quest/src/api/environment.cpp

@@ -482,6 +482,8 @@ void reportQuESTEnv() {
 
     /// @todo add function to write this output to file (useful for HPC debugging)
 
+    printer_sync();
+
     print_label("QuEST execution environment");
 
     bool statevec = false;
@@ -503,6 +505,8 @@ void reportQuESTEnv() {
 
     // exclude mandatory newline above
     print_oneFewerNewlines();
+
+    printer_sync();
 }
 
 

quest/src/api/matrices.cpp

@@ -763,11 +763,16 @@ void validateAndPrintMatrix(T matr, const char* caller) {
         structMem -= elemMem;
 
     size_t numBytesPerNode = elemMem + structMem;
+
+    printer_sync();
+
     print_header(matr, numBytesPerNode);
     print_elems(matr);
 
     // exclude mandatory newline above
     print_oneFewerNewlines();
+
+    printer_sync();
 }
 
 

quest/src/api/paulis.cpp

@@ -263,12 +263,16 @@ extern "C" void destroyPauliStrSum(PauliStrSum sum) {
 
 extern "C" void reportPauliStr(PauliStr str) {
 
+    printer_sync();
+
     // no header, so no indentation
     string indent = "";
     print_elemsWithoutNewline(str, indent);
 
     // print all user-set newlines (including none)
     print_newlines();
+
+    printer_sync();
 }
 
 
@@ -285,11 +289,15 @@ extern "C" void reportPauliStrSum(PauliStrSum sum) {
     // linearly with user input parameters, unlike Qureg and matrices.
     qindex numTotalBytes = numStrBytes + numCoeffBytes + numStrucBytes;
 
+    printer_sync();
+
     print_header(sum, numTotalBytes);
     print_elems(sum);
 
     // exclude mandatory newline above
     print_oneFewerNewlines();
+
+    printer_sync();
 }
 
 

quest/src/api/qureg.cpp

@@ -360,7 +360,8 @@ void reportQuregParams(Qureg qureg) {
 
     /// @todo add function to write this output to file (useful for HPC debugging)
 
-    // printer routines will consult env rank to avoid duplicate printing
+    printer_sync();
+
     print_label("Qureg");
     printDeploymentInfo(qureg);
     printDimensionInfo(qureg);
@@ -369,6 +370,8 @@ void reportQuregParams(Qureg qureg) {
 
     // exclude mandatory newline above
     print_oneFewerNewlines();
+
+    printer_sync();
 }
 
 
@@ -385,11 +388,15 @@ void reportQureg(Qureg qureg) {
     // include struct size (expected negligibly tiny)
     localMem += sizeof(qureg);
 
+    printer_sync();
+
     print_header(qureg, localMem);
     print_elems(qureg);
 
     // exclude mandatory newline above
     print_oneFewerNewlines();
+
+    printer_sync();
 }
 
 

quest/src/api/types.cpp

@@ -22,8 +22,12 @@ using std::string;
 void reportStr(std::string str) {
     validate_envIsInit(__func__);
 
+    printer_sync();
+
     print(str);
     print_newlines();
+
+    printer_sync();
 }
 
 extern "C" void reportStr(const char* str) {

quest/src/core/errors.cpp

@@ -41,6 +41,8 @@ using std::string;
 
 void raiseInternalError(string errorMsg) {
 
+    printer_sync();
+
     print(string("")
         + "\n\n"
         + "A fatal internal QuEST error occurred. "
@@ -49,6 +51,8 @@ void raiseInternalError(string errorMsg) {
         + "\n"
     );
 
+    printer_sync();
+
     exit(EXIT_FAILURE);
 }
 

quest/src/core/printer.cpp

@@ -32,6 +32,7 @@
 #include <stdlib.h>
 #include <iostream>
 #include <iomanip>
+#include <cstdio>
 #include <sstream>
 #include <memory>
 #include <vector>
@@ -167,6 +168,26 @@ void printer_setPauliStrFormat(int flag) {
 
 
 
+/*
+ * MULTI-PROCESS MANAGEMENT
+ */
+
+
+void printer_sync() {
+
+    // make all participating processes flush, to improve the chance
+    // that user-printing from non-root processes reaches the screen
+    // before QuEST begins to print from the root process
+    std::cout << std::flush; // C++ buffer
+    fflush(stdout);          // C buffer
+
+    // wait for all process flushes to complete, which defers non-root
+    // processes from printing until after root has finished printing
+    comm_sync();
+}
+
+
+
 /*
  * TYPE NAME STRINGS
  */

quest/src/core/printer.hpp

@@ -48,6 +48,14 @@ void printer_setPauliStrFormat(int flag);
 
 
 
+/*
+ * MULTI-PROCESS MANAGEMENT
+ */
+
+void printer_sync();
+
+
+
 /*
  * TYPE NAME STRINGS
  */

quest/src/core/validation.cpp

@@ -1142,6 +1142,10 @@ namespace report {
 
 void default_inputErrorHandler(const char* func, const char* msg) {
 
+    // force a std-flush and comm-sync so that the error message is not (well, less likely
+    // to be interrupted_ by users printing from a non-root process
+    printer_sync();
+
     // safe to call even before MPI has been setup, and ignores user-set trailing newlines.
     // It begins with \n to interrupt half-printed lines (when trailing newlines are set to
     // 0 via setQuESTNumReportedNewlines(0)), for visual clarity. Note that user's overriding
@@ -1153,7 +1157,7 @@ void default_inputErrorHandler(const char* func, const char* msg) {
 
     // force a synch because otherwise non-main nodes may exit before print, and MPI
     // will then attempt to instantly abort all nodes, losing the error message.
-    comm_sync();
+    printer_sync();
 
     // finalise MPI before error-exit to avoid scaring user with giant MPI error message
     // we always "take ownership" of MPI here since we're about to kill the whole program